<template>
  <div class="slider" ref="slider">
    <div class="slider-group" ref="sliderGroup">
      <slot></slot>
    </div>
    <div class="dots">
      <span class="dot" v-for="(item,index) in dots" :class="{active:currentIndex ===index}"></span>
    </div>
  </div>
</template>

<script>
  import {addClass} from "common/js/dom"
  import BScroll from 'better-scroll'

  export default {
    name: "slider",
    data() {
      return {
        dots: [],
        currentIndex: 0
      }
    },
    props: {
      loop: {
        type: Boolean,
        default: true
      },
      autoPlay: {
        type: Boolean,
        default: true
      },
      interval: {
        type: Number,
        default: 4000
      }
    },
    mounted() {
      setTimeout(() => {
        this._setSliderWidth()
        this._initDots()
        this._initSlider()
        if (this.autoPlay) {
          this._play()
        }
      }, 20)
      window.addEventListener("resize",()=>{
        if(!this.slider){
          return
        }
        this._setSliderWidth(true)
        this.slider.refresh()
      })
    },
    destroyed(){
      clearTimeout(this.timer)
    },
    methods: {
      _setSliderWidth(resize) {
        this.children = this.$refs.sliderGroup.children
        let width = 0
        let sliderWidth = this.$refs.slider.clientWidth
        for (let i = 0; i < this.children.length; i++) {
          let child = this.children[i]
          addClass(child, 'slider-item')
          child.style.width = sliderWidth + 'px'
          width += sliderWidth
        }
        if (this.loop && !resize) {
          width += 2 * sliderWidth
        }
        this.$refs.sliderGroup.style.width = width + 'px'
      },
      _initDots() {
        this.dots = new Array(this.$refs.sliderGroup.children.length)
      },
      _initSlider() {
        this.slider = new BScroll(this.$refs.slider, {
          scrollX: true,
          scrollY: false,
          momentum: false,
          snap: {
            loop: this.loop,
            threshold: 0.3,
            speed: 400,
          }
        })
        this.slider.on("scrollEnd", () => {
          let pageIndex = this.slider.getCurrentPage().pageX
          this.currentIndex = pageIndex
          if (this.autoPlay) {
            clearTimeout(this.timer)
            this._play()
          }
        })
      },
      _play() {
        this.timer = setTimeout(() => {
          let page = ++this.currentIndex;
          this.slider.goToPage(page % this.dots.length, 0, 400)
        }, this.interval);
      }
    }
  }
</script>

<style lang="stylus" rel="stylesheet/stylus">
  @import "~common/stylus/variable.styl"
  .slider
    min-height 1px
    .slider-group
      overflow hidden
      position relative
      white-space nowrap
      .slider-item
        box-sizing border-box
        float left
        overflow hidden
        text-align center
        a
          width 100%
          overflow hidden
          display block
          text-decoration none
        img
          display block
          width 100%
    .dots
      position absolute
      right 0
      left 0
      bottom 12px
      text-align center
      font-size 0
      .dot
        display inline-block
        width 8px
        height 8px
        border-radius 50%
        background $color-text-l
        margin 0 4px
        &.active
          width 20px
          border-radius 5px
          background $color-text-ll
</style>
